/*
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */

package voldemort.store.compress.lzf;


/**
 * Encoder that handles splitting of input into chunks to encode, calls
 * {@link ChunkEncoder} to compress individual chunks and combines resulting
 * chunks into contiguous output byte array.
 *<p>
 * Code adapted from H2 project (http://www.h2database.com) Java LZF
 * implementation by Thomas (which itself was inspired by original C code by
 * Marc A Lehmann)
 * 
 */
public class LZFEncoder {

    // Static methods only, no point in instantiating
    private LZFEncoder() {}

    /**
     * Method for compressing given input data using LZF encoding and block
     * structure (compatible with lzf command line utility). Result consists of
     * a sequence of chunks.
     */
    public static byte[] encode(byte[] data) {
        int left = data.length;
        ChunkEncoder enc = new ChunkEncoder(left);
        int chunkLen = Math.min(LZFChunk.MAX_CHUNK_LEN, left);
        LZFChunk first = enc.encodeChunk(data, 0, chunkLen);
        left -= chunkLen;
        // shortcut: if it all fit in, no need to coalesce:
        if(left < 1) {
            return first.getData();
        }
        // otherwise need to get other chunks:
        int resultBytes = first.length();
        int inputOffset = chunkLen;
        LZFChunk last = first;

        do {
            chunkLen = Math.min(left, LZFChunk.MAX_CHUNK_LEN);
            LZFChunk chunk = enc.encodeChunk(data, inputOffset, chunkLen);
            inputOffset += chunkLen;
            left -= chunkLen;
            resultBytes += chunk.length();
            last.setNext(chunk);
            last = chunk;
        } while(left > 0);
        // and then coalesce returns into single contiguous byte array
        byte[] result = new byte[resultBytes];
        int ptr = 0;
        for(; first != null; first = first.next()) {
            ptr = first.copyTo(result, ptr);
        }
        return result;
    }
}
